Device-to-device (D2D) cross link power control

ABSTRACT

Device-to-device (D2D) cross link power control systems and methods may be disclosed. For example, a device such as a UE or WTRU may determine whether it may have simultaneous transmissions where at least one of the transmissions may include a cross link transmission. The device may further determine whether a total transmit power of the simultaneous transmissions may exceed a maximum transmit power of the device. If the device may have simultaneous transmissions and such transmissions may exceed the maximum transmit power, the device may reallocate power based on a priority or priority setting. The device may further determine a maximum cross link power, a maximum device power, and a cross link transmit power level such that the device may further control the power for transmissions based thereon.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/906,063 filed on May 30, 2013, which claims the benefit of U.S.Provisional Patent Application Nos. 61/653,765 filed on May 31, 2012,and 61/785,033 filed on Mar. 14, 2013, each of which is incorporatedherein by reference.

BACKGROUND

Currently, when a device such as a UE engages in device-to-device (D2D)communication in connection with applications such as advanced topology(AT) applications, the device may operate two transmissions ortransmission links in parallel. For example, the device may operate anuplink transmission to a network component such as an eNB and anothertransmission such as a cross link (XL) transmission to another devicesuch as another UE. Unfortunately, management of the additional radiotransmission or link (e.g. the XL transmission or link in combinationwith the uplink) by the device may currently cause problems associatedwith scheduling between the links or transmissions, resource allocationof the links or transmissions, power control of the links ortransmissions, and the like.

SUMMARY

Cross link power control systems and methods (e.g. for device to device(D2D) architectures) may be disclosed. For example, a device such as aUE or WTRU may determine whether it may have simultaneous transmissionswhere at least one of the transmissions may include a cross linktransmission. The device may further determine whether a total transmitpower of the simultaneous transmissions may exceed a maximum transmitpower of the device. If the device may have simultaneous transmissionsand such transmissions may exceed the maximum transmit power, the devicemay reallocate power based on a priority or priority setting.Additionally, in embodiments, the device may further determine a maximumcross link power and a maximum device power such that the device mayfurther control the power for transmissions based thereon (e.g. thedevice may adjust the power of transmissions to not exceed the maximumdevice power and the power of the cross link transmission to not exceedthe maximum cross link power). The device may further determine a crosslink transmit power level such as a power level to transmit the crosslink transmission at (e.g. that may be below the maximum cross linkpower) and may further control the transmission power, for example, fortransmissions to another device based on the cross link power level.

The Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, not is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to the limitations that solveone or more disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the embodiments disclosed herein may behad from the following description, given by way of example inconjunction with the accompanying drawings.

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1D is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1E is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 2 illustrates diagrams of example embodiments of cross link channelmapping.

DETAILED DESCRIPTION

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application

Systems and/or methods for managing such as controlling power oftransmission links (e.g. an uplink and/or a cross link (XL)) in parallelor simultaneously may be provided. For example, in an embodiment, powercontrol may regulate both a maximum total cross link transmit power anda per-TTI dynamic transmit power of cross link physical control and datachannels, may administer the prioritized power reallocation betweensimultaneous uplink and/or cross link physical channels and signalsgiven a total device transmit power constraint, may manage the crosslink power headroom reporting coherently with the current uplink powerheadroom reporting based on the cross link measurements including pathloss, signal and interference strength, reference signal SINR and datachannel BLER, and the like as described herein.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. It is noted that the components,functions, and features described with respect to the WTRU 102 may alsobe similarly implemented in a base station.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 116. The RAN 104 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 104 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 104. TheRAN 104 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 104 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an lub interface.The RNCs 142 a, 142 b may be in communication with one another via anlur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 104 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 104 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 106.

The RAN 104 may include eNode-Bs 140 a, 140 b, 140 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 140 a, 140 b, 140c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 140 a, 140 b, 140 c may implement MIMO technology. Thus,the eNode-B 140 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 140 a, 140 b, 140 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 140 a, 140 b, 140 c may communicate with one another over an X2interface.

The core network 106 shown in FIG. 1D may include a mobility managementgateway (MME) 142, a serving gateway 144, and a packet data network(PDN) gateway 146. While each of the foregoing elements are depicted aspart of the core network 106, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 142 may be connected to each of the eNode-Bs 142 a, 142 b, 142 cin the RAN 104 via an S1 3interface and may serve as a control node. Forexample, the MME 142 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 144 may be connected to each of the eNode Bs 140 a,140 b, 140 c in the RAN 104 via the S1 interface. The serving gateway144 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 144 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 144 may also be connected to the PDN gateway 146,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 106 may facilitate communications with other networks.For example, the core network 106 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 106 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 106 and the PSTN 108. In addition, the corenetwork 106 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 104 and the core network 106according to an embodiment. The RAN 104 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 116. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 104, andthe core network 106 may be defined as reference points.

As shown in FIG. 1E, the RAN 104 may include base stations 140 a, 140 b,140 c, and an ASN gateway 142, though it will be appreciated that theRAN 104 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 140 a, 140 b,140 c may each be associated with a particular cell (not shown) in theRAN 104 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 116. In oneembodiment, the base stations 140 a, 140 b, 140 c may implement MIMOtechnology. Thus, the base station 140 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 140 a, 140 b, 140 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 142 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 106, and the like.

The air interface 116 between the WTRUs 102 a, 102 b, 102 c and the RAN104 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 106.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 106 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 140 a, 140 b,140 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 140 a, 140 b,140 c and the ASN gateway 215 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 100 c.

As shown in FIG. 1E, the RAN 104 may be connected to the core network106. The communication link between the RAN 104 and the core network 106may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 106 may include a mobile IP home agent(MIP-HA) 144, an authentication, authorization, accounting (AAA) server146, and a gateway 148. While each of the foregoing elements aredepicted as part of the core network 106, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 144 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 146 may be responsible for userauthentication and for supporting user services. The gateway 148 mayfacilitate interworking with other networks. For example, the gateway148 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 148 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 104may be connected to other ASNs and the core network 106 may be connectedto other core networks. The communication link between the RAN 104 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 104 and the other ASNs. The communication link betweenthe core network 106 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

As described herein, when a device such as a UE engages indevice-to-device (D2D) communication, the device may operate twotransmissions or transmission links in parallel. For example, the devicemay operate an uplink transmission to a network component such as an eNBand another transmission such as a cross link (XL) transmission toanother device such as another UE. Unfortunately, management of theadditional radio transmission or link (e.g. the XL transmission or linkin combination with the uplink) by the device may currently causeproblems associated with scheduling between the links or transmissions,resource allocation of the links or transmissions, power control of thelinks or transmissions, and the like.

To facilitate scheduling, resource allocation, power control, and/orother management operations between the links or transmission that maybe operated in parallel or simultaneously (e.g. an XL transmission andan uplink), power control systems and/or methods may be provided and/orused to regulate both the maximum total cross link transmit power andthe per-TTI dynamic transmit power of the cross link physical controland data channels, to administer the prioritized power reallocationbetween the simultaneous uplink and/or cross link physical channels andsignals given the total UE transmit power constraint, and to manage thecross link power headroom reporting coherently with the current uplinkpower headroom reporting based on the cross link measurements includingpath loss, signal and interference strength, reference signal SINR anddata channel BLER.

For example, in an example embodiment, a maximum total cross linktransmit power may be semi-statically configured by the network tooptimize the cross link spectrum and power efficiency and may manage theinter-cross-link interferences based on cross link power headroomreporting and signal and interference measurements. Additionally, adynamic cross link transmit power may be controlled on a per-TTI basisto achieve a semi-statically configured desired operating point with thehelp of the dynamic offsets calculated from transmission parameters suchas bandwidth, transport format, and Transmit Power Control (TPC)commands. The dynamic cross link power control may be centralized, forexample, performed by the network in a similar manner as the uplinkpower control in which a UE may calculate the sub-frame transmit powerusing the transmission parameters provided by the network via eitherPDCCH or RRC signaling. Alternatively, it may be distributed (e.g.performed by the UEs in the sense that the UEs may derive thetransmission parameters such as the TPC commands without the networkinvolvement). In an embodiment, one or more types (e.g. new types) ofpower headroom (PH) dedicated for the cross link may be triggered byevents (e.g. new events) specific to the cross link and reported to thenetwork in a new MAC Control Element or appended in the extended powerheadroom MAC control Element.

According to example embodiments, the systems and methods describedherein (e.g. the power control systems and/methods or mechanism) mayalso be applicable to both the network and UEs operating in a cellularLTE based system with the introduction of direct links between UEs.

For example, as described herein, user equipment (UE) transmit power ofphysical uplink control channel (PUCCH), physical uplink shared channel(PUSCH), and sounding reference signals (SRS) may be controlled by thenetwork to ensure that they may be received at the evolved nodeB (eNB)at sufficient signal to interference plus noise ratio (SINR) required bythe assigned transport formats. The uplink power control may also enablethe interference management and rate adaptation and may be performed perchannel for each serving cell while the serving cells may be carried ondifferent component carriers (e.g. in a carrier aggregation (CA)configuration). For example, the PUCCH and PUSCH of a primary cell(Pcell) may be power-controlled independently as well as the PUSCH ofthe Pcell and PUSCH of a secondary cell (Scell). The Pcell and Scellsassociated with a UE (e.g. when the UE may be in an RRC CONNECTED mode)may be defined as a set of serving cells for this UE. Additionally, inan embodiment, when CA may not be configured, a UE may have one servingcell that may be the primary cell.

In such an embodiment, although each component carrier transmit powermay be capped at the configured maximum per-serving-cell level ofP_(CMAX,c) (e.g. as described above), the sum of channel power mayexceed the maximum UE transmit power of P_(CMAX.) The P_(CMAX,c) andP_(CMAX) derivations may have been specified for non-CA and non-MIMOconfigurations, for CA configurations, and for MIMO configurations. Assuch, the transmit power reallocation and scaling may be performed basedon or according to a pre-defined priority setting of each channel. Forexample, when PUCCH and multiple PUSCH carrying user data may betransmitted simultaneously, the PUCCH may be first assigned with itspower-controlled level and the remainder of the power may be evenlydistributed to PUSCHs, which may lead to the need for a power scaling ofeach PUSCH if the rationed power level may be below the power-controlledlevel.

Additionally, the per-channel uplink power control may be a dynamicpower control system or method (e.g. mechanism) that may be applied on asub-frame basis and may include of an open-loop component and aclosed-loop component. The open-loop component may determine a coarsesemi-static operating point to achieve the SINR required by theconfigured transport format. As such, in an embodiment, the path lossand wide-band shadowing may be taken into consideration in the open-loopcomponent. Additionally, a UE may receive a nominal or desired powerlevel via higher layer signaling and may estimate the path loss based onthe reference signal received power (RSRP) measurement and the transmitpower of the cell specific reference (CRS) of the reference cell. Boththe reference cell and the CRS transmit level may be received via higherlayer signaling as well.

One or more dynamic offsets applied in the closed-loop component may beused to counter-act the small-scale multi-path condition andinterference variation. In an embodiment, a UE may calculate the dynamicoffsets based on the granted transmission bandwidth and/or MCS or thereceived explicit TPC commands. The transmission bandwidth and/or MCSmay be specified in a DCI format 0 and 4 in PDCCH, for example, usingC-RNTI. The TPC commands for the PUSCH may be received together with theassociated uplink grant in the DCI format 0 or 4 using TPC-PUSCH-RNTI.Additionally, the TPC commands for the PUCCH may be received togetherwith downlink scheduling in a DCI format 1/1A/2/2A using, for example,TPC-PUCCH-RNTI. In additional embodiments, the TPC commands may becarried without an uplink grant in DCI format 3/3A, for example, in ajoint manner (i.e. TPC commands for multiple UEs may be carried). TPCcommands that may be carried in DCI format 3/3A may be applied in theaccumulative mode in which the TPC commands may denote the changesrelative to the previous changes. The TPC commands may further beapplied in an absolute mode in which the TPC commands may denote thepower offset relative to the open-loop operating point regardless of theprevious received TPC commands.

According to an embodiment, for example, which may be enabled by thedirect UE-to-UE communications, Advanced Topology (AT) applications maybe provided and/or used as described herein. The AT applicationsdescribed herein may include an advanced topology-relay (AT-R) and anadvanced topology-local offload (AT-LO). In the AT-R application, aterminal UE (T-UE) may be able to exchange data with the network througha relay node which may be a Helper UE (H-UE). Additionally, the AT-LOapplication may enable the direct data communication between UEs inproximity under the control of the central network.

In an embodiment, the AT-R application may include one or more modessuch as a capacity mode and coverage mode. In, for example the capacitymode, the T-UE may be associated with the network and may enlist theH-UE to augment the radio link capacity and improve data transmissioncapacity. In, for example, the coverage mode the T-UE may be out ofnetwork coverage and may rely on an H-UE to obtain a networkassociation.

Additionally, according to an embodiment, a radio link (e.g. new radiolink) may be provided between a pair of T-UE and H-UE in the AT-Rapplications and a pair of UEs in the AT-LO application. Such a radiolink may be denoted as cross link (XL). The physical channels that maybe used on the XL may be OFDM-based and may be described herein.

In an embodiment, a Cross Link Physical Neighbor Discovery Channel(XPNDCH) may be provided and/or used. This channel may carry physicallayer sequences used for neighbor discovery beacon transmissionsincluding Neighbor Discovery Initiation Transmission (NDIT) and NeighborDiscovery Response Transmission (NDRT). Additionally, such a channel mayoccupy a default and pre-defined symbol and sub-carrier resourcelocation that may not be subject to cross link grants or schedulingand/or may apply code division multiple access and the codeconfiguration may be derived by a UE according to pre-defined techniquesand/or algorithms. According to an embodiment, when the cross linkbandwidth may be more than the default frequency resource pre-arrangedfor the neighbor discovery process, the network may allocate additionalsub-carriers (resources) for the channel to increase the neighbordiscovery capacity.

A Cross Link Physical Control Channel (XPCCH) may also be providedand/or used. This channel may carry the Cross Link Control Information(XCI) formats. Different XCI formats may be used for scheduling-relatedcontrol information, the Channel State Information (CSI), HARQ ACK/NACK,TPC Commands, Scheduling Requests (SR), and the like. In an embodiment,errors in the XCI may be e detected by appending CRC bits. The completeresource allocation of this channel may be determined by acentrally-controlled semi-static grant. XPCCH may apply space, time,frequency, or code division multiple access. In an embodiment, there maybe different types of XPCCHs defined as the design progresses and thediscussion pertaining to the power control can be applicable to each ofthe channels. Additionally, in a centralized scheduling scheme, thescheduling XCI may be carried in PDCCH and the feedback or HARQ relatedXCI may be carried in PUCCH/PUSCH and the XPCCH may not be applied.

According to another embodiment, Cross Link Physical Data Channel(XPDCH) may be provided and/or used. This channel may carry the crosslink user data received from the MAC layer. The complete resourceallocation of this channel may be determined by the H-UE cross linkgrant (XLG). XPDCH may apply space, time, frequency, code divisionmultiple access, and the like.

The cross link may carry cross link specific reference signals as well.Such signals may be used for cross link signal measurement, timing andfrequency synchronization, control channel estimation, and the like.Different physical channels may be multiplexed into different types ofcross link sub-frames.

According to an embodiment, a multiplexing scheme may be used asdescribed herein. In an embodiment, the multiplexing scheme may include,for example, time-multiplexing the XPCCH and XPDCH (e.g. the XPCCH andXPDCH may not be transmitted simultaneously). For example, themultiplexing may resemble that of PDCCH and PDSCH in a downlink such asa long term evolution (LTE) downlink. Additionally, the XPCCH may occupya number of symbol locations in the beginning of one sub-frame followedby the symbols allocated for the XPDCH. Based on the different powerlevels XPCCH and XPDCH may use or apply, time-multiplexing may reducethe cross link signal peak-to-average power ratio and may improve thepower amplifier efficiency. Time-multiplexing may also facilitate asequential decoding where scheduling information in the XPCCH may bedecoded first and the decoding of XPDCH may proceed when XPCCH decodingmay be successful. As such, in an embodiment, the receivingfunctionality may be switched off during the XPDCH duration (e.g. whenthe XPCCH indicates there may not be XPDCH data) to save battery power.The XPCCH and XPDCH power difference may further cause sub-carrier powerimbalance within one sub-frame and scaling may be needed to even it out.

The multiplexing scheme that may be used may also includefrequency-multiplexing of the XPCCH and XPDCH. Such a scheme may be useddue to the relatively low cross link transmit power. For example, themultiplexing may be similar to that of an uplink such as an LTE uplink.In such an embodiment, both the XPCCH and XPDCH may span over a TTI(e.g. an entire TTI) on different sub-carriers and, thus, may betransmitted simultaneously. In this case, power reallocation may beprovided and/or used based on whether (e.g. if) a total power may exceeda maximum cross link power. Additionally, in such an embodiment, the UEmay not be able to decode the XPCCH completely and/or receive or aquirescheduling information until the end of the TTI. As such, the UE maybuffer the DPDCH to decode after the XPCCH decoding may be done.

According to an additional embodiment, the multiplexing scheme mayinclude code-multiplexing the XPCCH and XPDCH (e.g. in a similar manneras the uplink DPCCH/DPCCH in WCDMA systems). In such an embodiment, thechannels may span over one TTI and may use the same frequency resources,but they may apply different orthogonal spreading codes. Additionally,in such an embodiment, buffering of the DPDCH data may be increasedcompared to the time-multiplexing scheme.

Additionally, as described herein, a MAC layer and/or a PHY layer may beprovided and/or used. The MAC layer may provide services to the RadioLink Control (RLC) in the form of logical channels. The type of logicalchannel may be either a control channel used for transmission of controland configuration information or a traffic channel used for carrying theuser data. The cross link logical channels may include PCCH, XCCCH, DCCHand DTCH.

The PHY layer that may offer services to the MAC in the form oftransport channels and the cross link transport channels may includeXPCH, XCCH and XL-SCH. Data on a transport channel may be organized intotransport blocks and normally in each TTI one transport block of acertain size may be transmitted. In the case of spatial multiplexing(e.g. MIMO), up to two transport blocks may be transmitted in one TTI. Apreliminary example of channel mapping between logical, transport andphysical channels on the cross link may be depicted in FIG. 2, whichillustrates diagrams of example cross link channel mapping.

As described herein, when a UE may engage in UE-to-UE communication inconnection with AT applications, it may operate two transmissions inparallel. One may be the uplink transmission to the eNB and the othermay be the cross link transmission to the other UE. The UE transmitpower may be considered as a type of shared resource between channelsoperating on the two radio links, which may use a power control systemand/or method described herein that may execute and coordinate the powercontrol of each radio link transmission. The cross link transmissionpower control may be integrated into the existing uplink power controlto handle (e.g., the power reallocation and power headroom reporting).

Additionally, the cross link (XL) may share the frequency band appliedon the LTE downlink or uplink, for example, an in-band configuration, oradopt a different frequency band that may be separated from the LTEband, for example, an out-of-band configuration. Both configurations mayencounter different types of interference such as in-device interferencebetween the cross link and LTE downlink or uplink operation, in-airinterference between the cross links and the LTE downlinks or uplinks inproximity, in-air interference between the cross links in proximity, andthe like. In an embodiment, the out-of-band configuration may not besubject to as much in-device and in-air interference between the crosslinks and LTE links (e.g. since an out-of-band configuration normallymay apply adequate frequency spectrum isolation between the cross linkband and LTE bands). Thus, in such an embodiment, a device may operatetwo radio chains each with its own baseband processing and independentFFT.

While in-device interference may be handled primarily with the physicalradio component of a device, the in-air interference may further becoordinated and reduced with the help of cross link power control.Moreover, the cross link power control may be used to counteract thedynamic propagation conditions of the cross link to achieve the receivedenergy per bit provided and/or used by the cross link QoS whilefacilitating battery preservation.

As described herein, to help manage two transmission links, powerreallocation (e.g. at a UE) may be provided and/or used. For example, inan embodiment, power control may be performed independently andseparately for each physical channel, and when multiple channels may betransmitted in parallel (e.g. simultaneous PUCCH and PUSCH), a totaltransmit power such as a sum of the power-controlled power of eachphysical channel may exceed a maximum UE transmit power P_(CMAX.) Tohelp control the total transmit power from exceeding the maximum UEtransmit power, a power reallocation scheme among PUCCH and PUSCHsaccording to a pre-defined priority setting may be executed (e.g. via anuplink power control mechanism).

For example, when a UE may have simultaneous PUCCH, PUSCH with UCI onone serving cell and PUSCHs without UCI in the other serving cells, andthe total transmit power of the UE may exceed P_(CMAX) (i), the UE mayreallocate the power associated with such transmissions based on apriority. According to an example embodiment, the power may bereallocated according to the priority: (1) PUCCH, (2) PUSCH with UCI,and (3) PUSCH without UCI. Thus, the PUCCH may be assigned first withits power-controlled power and the remainder may be assigned to thePUSCH with UCI as shown below in the equation. In one embodiment, theP_(PUSCH with UCI(i)) may be the power-controlled power of the PUSCH.P _(PUSCH with UCI)(i)=min {P _(PUSCH with UCI)(i), (P _(CMAX)(i)−P_(PUCCH)(i))}[dBm]Additionally, in an embodiment, the remainder thereof (e.g. what may beleft of the total power) may be evenly distributed to the PUSCHs withoutUCI. The scaling factor w(i) may be applied to adjust the PUSCH powerrelative to its power-controlled level to ensure the total transmitpower may not exceed P_(CMAX) (e.g. as shown by the following equation).Σw(i)×P _(PUSCHs without UCI)(i)=P _(CMAX)(i)−P _(PUCCH)(i)−P_(PUSCH with UCI)(i))[dBm]The same priority may apply for simultaneous transmission of other PUCCHand PUSCH combinations (e.g. PUCCH and PUSCHs without UCI and PUSCH withUCI and PUSCHs without UCI).

For a device-to-device (D2D)-capable UE, the power reallocation mayinclude handling or managing cross link physical channels, for example,since the cross link transmission may share the P_(CMAX) with the uplinktransmission. Different power reallocation schemes that may include ortake into account the cross link may be used for differentconfigurations with regard to simultaneous XL and UL transmissions andalso simultaneous XPCCH and XPDCH transmission. For example, the uplinktransmission and cross link transmission may be scheduled exclusively(e.g. no simultaneous uplink and cross link transmissions in a givensub-frame). Such a scheduling may help address certain interferenceissues particularly for the uplink in-band configuration where the crosslink applies the uplink sub-carrier resources. The power reallocationscheme may also be simplified, for example, as it may handle UL channelsor XL channels in a given sub-frame (e.g. not both).

The simultaneous UL and XL transmission may also occur in the case wherea UE may either transmit a preamble or a PUSCH carrying MSG3 in anon-going RACH procedure. The MSG3 transmission may be scheduled by theshortened uplink grant carried in a Random Access Response (RAR) inresponse to the RACH preamble. The RACH procedure described herein maybe used in one or more of the following: to send new uplink data orcontrol information, e.g. an event-triggered measurement report, when aUE may be in a RRC CONNECTED state but may not be uplink-synchronized;to transmit HARQ acknowledgement in the uplink when a UE may be in a RRCCONNECTED state, receives new downlink data, but may not beuplink-synchronized; to handover to a target cell when a UE may be inRRC CONNECTED state; to transition from a RRC IDLE state to a RRCCONNECTED state, e.g. tracking area update; to recover from a radio linkfailure (RLF); and the like.

According to an example embodiment, a XL transmission may occur, forexample, when a UE may be in a RRC CONNECTED state, but may not beuplink-synchronized and uplink or control information may be sent and/orwhen a UE may be in RRC CONNECTED state and HARQ may be transmitted inan uplink. In such an embodiment, simultaneous UL and XL transmissionmay include the simultaneous transmission of XL and the PRACH (e.g.preamble) as well as the PUSCH carrying MSG3. Thus, the powerreallocation may further take into account PRACH and PUSCH carryingL1/L2 control signaling, which, for example, may include both PUSCHcarrying UCI and PUSCH carrying MSG3. In addition, the UL SRStransmission may occur simultaneously with XL transmission.

Additionally, the power reallocation may take into consideration thesimultaneous XPCCH and XPDCH transmission. For example, in anembodiment, the XPCCH may be transmitted without XPDCH (e.g. whencarrying a XCI for channel state feedback or a HARQ acknowledgement).XPDCH may also be transmitted alone (e.g. when the schedulinginformation of the XPDCH may be centrally controlled by the networkwhich informs both UEs in the AT application via a downlink DPCCH). Assuch, according to an example embodiment, the UEs may transmit the XPDCHwithout accompanying control information.

According to an additional embodiment, XPNDCH may not be powercontrolled and may instead be transmitted with a pre-configured commonpower level such that UEs may derive path loss information from aneighbor discovery process. Moreover, XPNDCH may not be transmittedsimultaneously with XPCCH or XPDCH. Based on the neighbor discoveryprocess in an application such as an AT application, the XPNDCH may begiven highest priority when simultaneously transmitted with ULtransmission.

As such, based on the embodiments described herein, a preliminary powerreallocation with XL may apply a priority setting as listed in Table 1below.

TABLE 1 Power Reallocation with XL No simultaneous XPCCH andSimultaneous XPCCH and Configurations XPDCH XPDCH With XPNDCH No ULchannel power reallocation UL channel power reallocation- UL channelpower simultaneous according to Rel10 rules. according to Rel10 rules.reallocation according to Rel10 XL No XL channel power reallocation XLchannel power allocation in rules. and UL (either XPCCH or XPDCH in onethe order of No XL channel power sub-frame) 1. XPCCH reallocation(XPNDCH) 2. XPDCH Simultaneous The combined UL/XL channel The combinedUL/XL channel The combined UL/XL channel XL power allocation in theorder of power allocation in the order of power allocation in the orderof and UL 1. PUCCH 1. PUCCH 1. XPNDCH 2. PUSCH with L1/L2 2. PUSCH withL1/L2 2. PUCCH control signaling control signaling 3. PUSCH with L1/L23. XPCCH 3. XPCCH control signaling 4. PUSCH without L1/L2 4. PUSCHwithout L1/L2 4. PUSCH without control signaling control signaling L1/L2control 5. SRS 5. XPDCH signaling and 6. SRS 5. SRS 1. PRACH and and 2.XPCCH 1. PRACH 1. XPNDCH in sub-frames with XPCCH and 2. XPCCH 2.PRACH 1. PUCCH 3. XPDCH Note the XPNDCH can be set 2. PUSCH with L1/L2at a low power level and its high control signaling prioritization mayhave a small 3. PUSCH without L1/L2 impact on the UL transmission.control signaling 4. XPDCH 5. SRS and 1. PRACH 2. XPDCH in sub-frameswith XPDCH.

The total power therefore may be assigned according to the prioritysetting to each present physical channel and the power level determinedby the power control of each physical channel may be scaled inaccordance with the availability of the power resources.

The power reallocation (e.g. the result thereof or output therefrom) mayalso be used to handle the power imbalance between UL and XLtransmission when both links may share the same power amplifier (PA),for example, for an in-band cross link configuration. For example, theUL and XL transmissions may use different uplink sub-carriers, but maypass through the same PA and a large difference between the power of ULsub-carriers and that of XL sub-carriers may degrade the PA efficiency.After the power reallocation, a UE may report such a power imbalance asa type of event such as a new pre-defined event when, for example, thepower difference may exceed a pre-set threshold. According to anembodiment, network scheduling may take this power imbalance intoconsideration and adjust the uplink grant or/and the XL maximum transmitpower decision to correct the situation. Additionally, in response to alarge power difference between the UL and XL sub-carriers, themultiplexing of UL and XL may be changed from simultaneous to timemultiplexed.

In an embodiment, a XL and/or UE maximum power may be provided and/orused. For example, a UE and/or network component may determine an XLand/or UE nominal maximum power. In such an embodiment, the total sum ofthe multiple physical channels that may be transmitted in parallel ondifferent component carriers and/or different links (UL/XL) overtransmitting antennas or a portion thereof (e.g. XL may have dedicatedantennas) may not exceed the maximum power P_(CMAX.) Also, the powercontrol may be first capped at the maximum transmit power configured atthe component carrier level, i.e. P_(CMAX,c.) A UE in the ATapplications may set the cross link maximum power P_(CMAX,XL) accordingto the following equations:

     P_(CMAX _ L, XL) ≤ P_(CMAX, XL) ≤ P_(CMAX _ H, XL)      andP_(CMAX _ L, XL) = MIN{P_(EMAX, XL) − Δ T_(C, XL), P_(PowerClass) − MAX(MPR_(XL) + AMPR_(XL) + Δ T_(1 B, XL), PMPR_(XL)) − Δ T_(C, XL)}P_(CMAX _ H, XL) = MIN{P_(EMAX, XL), P_(PowerClass))where P_(EMAX,XL) may be the value given by IE P-Max. In an embodiment,such a configuration may be used on a per-carrier frequency and thecross link may be configured similarly. P_(PowerClass) may be themaximum UE power. The cross link Maximum Power Reduction MPR_(XL) andAdditional Maximum Power Reduction AMPR_(XL) may be specifically for theXL band configuration or if applicable the values for XL in-bandconfiguration and for XL out-of-band configuration may be used.Power-management Maximum Power Reduction PMPR_(XL) may be the cross linkspecific power management term based on the XL band selection.Additionally, ΔT_(C,XL) may be 1.5 dB or 0 dB when a parameter (e.g. asdescribed herein) may apply to the cross link band. ΔT_(1B,XL) an may beadditional tolerance for the cross link.

To determine the total UE maximum power P_(CMAX,) different UL and XLconfigurations may be taken into consideration as described herein. Forexample, simultaneous UL and XL transmission may not be taken intoconsideration. In such an embodiment, for the UL transmissionsub-frames, the P_(CMAX) may be calculated as described herein oraccording to current specifications such as a 3GPP Rel-10 specification.Additionally, in the XL transmission sub-frames, P_(CMAX) _(_)_(L)≤P_(CMAX)≤P_(CMAX) _(_) _(H)whereP_(CMAX) _(_) _(L)=P_(CMAX) _(_) _(L,XL)P_(CMAX) _(_) _(H)=P_(CMAX) _(_) _(H,XL)The UE maximum power may, thus, be either the maximum uplink power orthe maximum cross link power in their respective transmissionsub-frames.

Additionally, simultaneous UL and XL transmission may be taken intoconsideration (e.g. to determine the UE maximum power). In such anembodiment, for XL in-band configuration, the cross link may be aspecial case of intra-band carrier aggregation with multiple servingcells. Furthermore, the UL and XL may have identical MPR, AMPR and/orPMPR values and the P_(CMAX) may be

     P_(CMA _ L) ≤ P_(CMAX) ≤ P_(CMAX _ H)      whereP_(CMAX _ L) = MIN{10 log  10(∑P_(EMAX, c) + P_(EMAX, XL)) − MAX(Δ T_(C, XL), Δ T_(C, c)), P_(PowerClass) − MAX(MPR + AMPR, PMPR) − MAX(Δ T_(C, XL), Δ T_(C, c))}     P_(CMAX _ H) = MIN{10 log  10(∑P_(EMAX, c) + P_(EMAX, XL)), P_(PowerClass)).The summation of P_(EMAX,C) may include the UL CA intra-bandconfiguration and the P_(EMAX) values may be converted to linear scalefrom the dBm scale may be used in the RRC signaling for the summation.Also, the total may be converted back to dBm value for one or moreadditional operations. The ΔT_(C) value that may be used may take thehighest of the uplink serving cells and the cross link.

In such an embodiment, for an XL out-of-band configuration, the crosslink may be a special case of inter-band carrier aggregation withmultiple serving cells. Additionally, the UL and XL may have differentMPR, AMPR and PMPR values and the P_(CMAX) can be

P_(CMAX_L) ≤ P_(CMAX) ≤ P_(CMAX_H) whereP_(CMAX_L) = MIN{(∑ P_(CMAX, c) + P_(CMAX, XL)), P_(PowerClass)}P_(CMAX_H) = MIN{10 log₁₀(∑ P_(EMAX, c) + P_(EMAX, XL)), P_(PowerClass)}andP_(CMAX, XL) = MIN{P_(EMAX, XL) − Δ T_(C, XL), P_(PowerClass) − MPR_(XL) − AMPR_(XL) − Δ T_(C, XL) − Δ T_(1B, XL), P_(PowerClass) − PMPR_(XL) − Δ T_(C, XL)}P_(CMAX, c) = MIN{P_(EMAX, c) − Δ T_(C, c), P_(PowerClass) − MPR_(c) − AMPR_(c) − Δ T_(C, c) − Δ T_(1B, c), P_(PowerClass) − PMPR_(c) − Δ T_(C, c)}The parameter definitions may also be the same as those applied in, forexample, the P_(CMAX,XL) calculation.

As such, a UE such as a UE running an AT application may derive theP_(CMAX,XL) and P_(CMAX) as described herein (e.g. above) based on theUE's power class, the signaled maximum power, one or more of the MPR,AMPR, and/or PMPR that may be applicable to the UL band and the XL band,and/or the tolerances that may be used.

Additionally, in an example embodiment, XL maximum power control may beprovided and/or used to manage the power control associated withsimultaneous transmissions or links. For example, a nominal cross link(XL) maximum power P_(CMAX ,XL) may be determined by the UE and/or anetwork component. According to an embodiment, the XL maximum powerP_(CMAX,XL) may be determined (e.g. calculated) in a similar manner as acomponent carrier maximum power. However, the cross link may have adifferent interference situation than that of the uplink and, as such,the cross link maximum power may be used by the network to optimize thecross link resource utilization efficiency and coordinateinter-cross-link interferences. For example, two neighboring or close-bycross links may be allocated with identical resources as long as themaximum power of both cross links may be controlled so as not tointerfere with each other. The XL maximum power control (XLMPC) may thusbe used to facilitate space division multiple access (SDMA) for crosslinks.

According to an embodiment, the XLMPC may apply an additionalsemi-static power control on the P_(CMAX,XL) such that the determinedmaximum XL power or nominal level, P_(CMAX,XL), may be the upper boundfor XLMPC and the applicable maximum XL power level (e.g. that may besignaled or established by the network as described herein such as asemi-static value derived by a network algorithm or calculated orreported based on metrics of the XL) may be controlled and signaled bythe network in a semi-static fashion. The XLMPC may be particularlyuseful in a semi-static grant scheme where the dynamic per-TTIscheduling and power control may be performed or done by the UEs.

Additionally, the XL maximum power level may be updated to, for example,maximize the capacity of certain XLs given the operational conditions interms of the interference level, battery level, power head room, XLchannel state information, a long-term XL capacity reporting in terms ofachieved spectral efficiency in terms of bit/s/Hz (e.g. which may eitherbe short-term such as per TTI value or long-term such as an averagelong-term power headroom) as described herein (e.g. below). To updatethe XL maximum power level, at least one of the following may besignaled to a UE. For example, in one embodiment, a P-Max informationelement (IE) in a dedicated RRC signaling may be used and/or reusedwhere the adjustment of P-Max may lead to a new P_(CMAX,XL) based on oneor more calculates (e.g. a suitable calculation as described herein).

According to another example, an explicit maximum XL power level in asemi-static grant in connection with a semi-static scheduling scheme ofthe cross link may be signaled. In such an embodiment, the maximum XLpower level may be included in or part of the resources that may beallocated to the cross link in the cross link grant. The grant, whichmay be the P_(CMAX,XL) level, may be carried in dedicated RRC signaling,a new MAC CE, new DCI formats in PDCCH, and the like.

In another example embodiment, an explicit maximum XL power level in aRRC IE such as a new RRC IE including, for example, aCrossLinkPowerControl element may be used to signal semi-staticparameters that may be provided in XL dynamic power control (XLDPC).According to an embodiment, the new IE may reuse the structure of RRC IEUplinkPowerControl. Additionally, the XLMPC and XLDPC parameters (e.g.at least a portion thereof) may be carried in dedicated RRC signaling.

According to an additional example embodiment, an initial value in theRRC dedicated signaling may be provided and/or used to signal a XLmaximum power level. In such an embodiment, a DCI format such as a newDCI format to carry relative adjustment commands similar to the TPC bitsmay subsequently be used and/or provided to adjust the XL maximum powerlevel.

As such, in example embodiments, the XLMPC may operate at a slower ratethan the XLDPC, but it may enable the cross link maximum power level tobe updated more often than the current component carrier maximum powerlevel may be. This may provide the network with more flexibility inmanaging the cross links.

Additionally, the XLMPC may be determined by one or more algorithms atthe eNB based on a range of parameters including, for example, theavailable cross link bandwidth, QoS request, buffer status, interferencemeasurement, cross link capacity (bits/Hz/s), power headroom, batterylevel, etc. For example, in the case of semi-statically allocatedresources, the network may maintain, on average, a small positive powerheadroom to ensure the UE may achieve the required throughput withoutusing excessive power. Also, if a cross link may be assigned with morebandwidth, the maximum power level may be increased accordingly.

Based on a semi-static nature of the XLMPC, long-term measurements mayfurther be reported by the UE to support the feature. For example, thefiltered or averaged cross link signal and interference measurement mayprovide the network with information about potential interfering crosslinks whose maximum cross link power may be reduced. Also, a long-termaverage power headroom, especially in the case of semi-static schedulingwith fixed bandwidth, may inform the network whether the assignedmaximum cross link power may be used efficiently.

Such long-term measurements may be requested, configured, and reportedsimilar to the RRC type measurements carried in uplink data channel. Thenetwork may assign an uplink grant for the reporting when themeasurement may be requested.

In an embodiment, the XLMPC may regulate the maximum cross link powerand may not affect the XLDPC that may operate on a per-TTI basis (e.g.except by changing the level where the cross link transmit power may becapped). As such, the cross link power control, especially when thecross link applies semi-static scheduling, may have at multiple (e.g.two) levels of power control. A first level of power control may includethe cross link maximum power control (XLMPC) where a P_(CMAX,XL) levelmay updated by the eNB and applied in a pre-arranged period such as on asemi-static basis. In such an embodiment, the nominal P_(CMAX,XL) may bethe upper bound, i.e. the network may not configure a P_(CMAX,XL) higherthan the nominal level.

A second level of power control may include the cross link dynamic powercontrol (XLDPC) where a cross link physical channel that may transmitpower per TTI may be calculated per cross link physical channelaccording to a pre-defined algorithm. In such an embodiment, the sum ofthe transmit power of physical channels may not exceed the maximum levelregulated by the XLMPC or power reallocation and scaling within thecross link may be performed.

As described herein, such embodiments may provide a centralized and/or asemi-static distributed scheduling scheme. In the centralized dynamicscheduling scheme, the network may accordingly perform the dynamic powercontrol and may not need the XLMPC. In this case, the nominalP_(CMAX,XL) may be used without semi-static adjustment.

In the semi-static distributed scheduling, the power control may beadministered to facilitate an efficient utilization of power resourcesby the adjustment of the maximum cross link power while maintaining theQoS. For example, a transmitting UE may calculate a maximum MCSaccording to the assigned maximum power and the dynamic power controlformula when the assigned bandwidth may be applied unchanged. Thesubsequent data transmissions may result in a BLER ratio for apre-defined period measured at the receiving UE. The receiving UE maygenerate TPC commands based on the BLER ratio to regulate the power anda consecutive number of unidirectional TPC commands may trigger a powerhead room reporting (PHR). For example, when the power may be more thanrequired to deliver the MCS, the receiving UE may send a number ofconsecutive DOWN TPC commands, which may be pre-defined as a PHR triggerand the transmitting UE may report the power headroom to the eNB, whichmay in turn reduce the maximum cross link power in the next grant.Alternatively, a threshold of power adjustment in a specified period oftime may be used to trigger PHR. This may enable PHR to occur even whenthe power adjustment may not be monotonic.

Additionally, XL dynamic power control may also be provided and/or used.For example, depending on whether or not a UE may have autonomy inexecuting the functionality, the cross link dynamic power control(XLDPC) may have two schemes. In a centralized XLDPC (C-XLDPC) scheme,UEs may not be given autonomy. The XL transmission may occur uponreceiving an XL grant issued on a sub-frame basis. The cross linkphysical channels may be power-controlled in a similar manner as whatmay be specified in LTE baseline uplink power control. The cross linkmay be a special case of a component carrier. Additionally, in such anembodiment, the UE may not have autonomy in determining power controlparameters and may calculate the transmit power based on parametersreceived from the network. The scheme may be tied to a dynamic per-TTIand centralized scheduling scheme and the XPCCH may not be applicable.

In a distributed XLDPC (D-XLDPC), UEs may be given a certain degree ofautonomy. The cross link transmission may be granted and configured bythe network on a semi-static basis. During the semi-static period, a UEmay autonomously perform cross link dynamic power control such that theUEs may derive the used required parameters (e.g. at least a portionthereof) in calculating the channel transmit power. For example, the UEmay derive and transmit TPC bits or may determine the desired targetpower level (used as the open loop operating point) based oninterference measurements. This scheme may further be tied to asemi-static and distributed scheduling scheme described herein. Bothschemes may use one or more of the power control parameters describedherein.

Additionally, an XPDCH power determination may be made and/or used. Forexample, in an embodiment, the XPDCH transmit power of sub-frame i maybe calculated according to the equation or equations below. Inparticular, in an embodiment, the XPCCH power subtraction may beapplicable when the XPCCH and XPDCH may be transmitted simultaneouslyand may be calculated as follows:

P_(XPDCH)(i) = min {P_(CMAX, XL), 10 log₁₀(BW_(XPDCH)(i)) + P_(O _ XPDCH) + α_(XL)PL + Δ_(TF _ XL)(i) + TPC_(XL)}[dBm]     orP_(XPDCH)(i) = min {P_(CMAX, XL) − P_(XPCCH)(i), 10 log₁₀(BW_(XPDCH)(i)) + P_(O _ XPDCH) + α_(XL)PL + Δ_(TF _ XL)(i) + TPC_(XL)}[dBm]In an example embodiment, the P_(CMAX,XL) may be set as described hereinor semi-statically controlled. Additionally, the bandwidth,BW_(XPDCH)(i) may be the transmission bandwidth scheduled in sub-framei. According to an embodiment, the bandwidth may be specified in thedynamic per-TTI XL grant or semi-static grant. Furthermore, P_(O) _(_)_(XPDCH) , which may be the nominal power level, may be a desired and/ortarget UE specific power level given the interference level. The crosslink path loss, PL, may be estimated by the UEs where α_(XL) may be thefractional path loss compensation factor, which for uplink power controlmay be used by the network to trade-off between the uplink schedulingfairness and total cell capacity and/or the full path loss compensation(i.e. α_(XL)=1) may maximize the fairness for cell-edge UEs at theexpense of higher inter-cell interference. In an embodiment, such afeature may not be applicable to the cross link, but the parameter maybe kept for further consideration. Additionally, the value of P_(O) _(_)_(XPDCH) +PL may denote the basic open loop operating point. TheΔ_(TF,XL)(i) may be a pre-defined function that derives the requiredBPRE based on assigned number of block, block size, assigned number ofresource elements, Kr, Ks, etc. It may, in an embodiment, give thedesired power to achieve the SINR given the Transport Format (TF)scheduled in the sub-frame i. TPC_(XL) may be a dynamic offset algorithmeither being accumulative or absolute with pre-defined power adjustmentstep based on the received TPC commands for XPDCH.

Additionally, in an embodiment, the initial P_(XPDCH) may be based onthe initial scheduled transmission parameters. For example, when thecross link may be established, the UEs may start with transmitting thecross link reference signal. Such a cross link reference signal may beused for XPCCH channel estimation and also for cross link CSIgeneration. In a centralized scheduling scheme, the CSI that may bereported to the network in the UL may be used to derive the initial XLgrant including the bandwidth and the MCS. The UE, upon receiving thegrant, may calculate the initial power accordingly. Such a cross linkreference signal may also be used with a distributed scheduling scheme.In such an embodiment, the UE may determine the bandwidth and the MCSbased on the CSI reported on the XL.

When the P_(XPDCH) may exceed the P_(CMAX,XL) the P_(CMAX,XL) may beused such that the XPDCH power level may be scaled down. Also, in anembodiment, when simultaneously transmitted with XPCCH, the XPDCH may bescaled down when the remainder of cross link power after XPCCH powerassignment may be less than the P_(XPDCH) . When performing and/orproviding XLDPC, a UE may detect the wind-up effect with the help ofpre-defined criteria such as a minimum and/or maximum power detection.

According to another embodiment, an XPCCH power determination may bemade and/or used. For example, the XPCCH transmit power of sub-frame imay be calculated according to the following:P _(XPCCH)(i)=min{P _(CMAX,XL)(i),P _(O) _(_) _(XPCCH) +PL+Δ _(TF) _(_)_(XL)(XCI)+TPC _(XL)}[dBm]where the P_(CMAX,XL) may be suitably set or semi-statically controlled.P_(O) _(_) _(XPCCH) (i.e. the nominal power level) may be thedesired/target UE specific power level given the interference level.This power level may be different than the P_(O) _(_) _(XPDCH). Thecross link path loss, PL, may be estimated by the UEs. The same pathloss may be used for both XPDCH and XPCCH power control. Additionally,control channels may normally apply full path loss compensation. Thevalue of P_(O) _(_) _(XPDCH)+PL may denote the basic open loop operatingpoint, which may differ from that of the XPDCH, as the XPDCH and XPCCHmay have different multiple access schemes and also different targetlevels. The Δ_(TF,XL)(i) may be a pre-defined function that may derivethe BPRE based on the pre-defined XCI format carried in XPCCH (e.g. thenumber of information bits) the number of CRC bits, coding rate, and thelike. In an embodiment, the Δ_(TF,XL)(i) may give the power to achievethe target error rate for the XPCCH format carried in the sub-frame i.Additionally, TPC_(XL) may be a dynamic offset algorithm either beingaccumulative or absolute with pre-defined power adjustment step based onthe received TPC commands for XPCCH.

In such an embodiment (e.g. to determine XPCCH power), the initial XPCCHpower level may start with the open loop operating point plus thedynamic offset corresponding to the XCI format. Alternatively, theinitial XPCCH power level may add another pre-defined offset to ensuresuccessful initial XPCCH reception before the channel condition andinterference situation may be reported.

Additionally, there may be certain type of XPCCH that may not apply theXLDPC. For example, the XPCCH may carry the XLDPC parameters such theP_(O) _(_) _(XPCCH), the TPC bits, and the like. This type of XPCCH mayapply the XLMPC (i.e. may be transmitted with a configured allowedmaximum cross link power).

An XLRS power determination may also be made and/or used as describedherein. According to an example embodiment, a XLRS may include one ordifferent types of reference symbols (RS). For example, the XLRS may bee.g. XL specific RS (XLSRS) that may be transmitted when the cross linkmay be established. Such a XLRS may be applied for a variety of purposesincluding cross link signal measurement, channel estimation for XPCCHdecoding, initial cross link timing acquisition, and the like. In suchan embodiment, the XLRS may not apply XLDPC. Instead, it may betransmitted with a fixed power level configured when the cross link maybe established (e.g. at P_(CMAX,XL) where it may follow the XLMPC thatmay be applied). There may be also demodulation RS (DMRS) transmittedtogether with XPDCH to help with XPDCH decoding. Such demodulation RSesmay be set at the same power as the P_(XPDCH) controlled by the XLDPC.

As described herein, a nominal power level may be provided and/or usedin an embodiment. For example, the P_(O) _(_) _(XPDCH) and P_(O) _(_)_(XPCCH) may denote the desired or target power level that may be usedfor certain BLER operating point. They may be set, for example, based onthe received interference level and thermal noise power.

In a C-XLDPC scheme, the network semi-statically may provide the P_(O)_(_) _(XPCCH) and P_(O) _(_) _(XPDCH) in the dedicated RRC signalingsimilarly as the equivalent nominal power level used in uplink powercontrol. For the network to determine the nominal levels, the UEs mayreport the received interference level and thermal noise power invarious (e.g. new) types of RRC measurement reporting carried in PUSCH.The measurements may be similar to the LTE uplink receive interferenceand thermal noise power measurements. The network may request andconfigure the measurements and may provide uplink grant for themeasurement result reporting.

In a D-XLDPC scheme, the UEs in the AT application may determine thenominal levels autonomously. The same interference level and thermalnoise measurements may be applied and based on the measurement resultsthe UE may derive the P_(O) _(_) _(XPDCH) and P_(O) _(_) _(XPCCH) andmay send them over the cross link in XPCCH. Given the semi-static natureof this parameter, it may also be transmitted in XPDCH using a new MACControl Element or via RRC signaling.

A transmission format (TF) may further be provided and/or used. Thetransmission format (TF) may include the bandwidth and MCS which may beapplied in the power calculation to ensure the resulting power mayprovide the required SINR. In a C-XLDPC scheme, the TF may betransmitted as described below.

In an example embodiment, the TF may be transmitted by cross linkcontrol information (XCI) format carried in a PDCCH. The XCI and DCI maybe both decoded with C-RNTI. Additionally or alternatively, the XCI mayapply a XL-RNTI.

The TF may further be transmitted in DCI format 0 or DCI format 4 (e.g.with multi-antenna port transmission). Such an embodiment may enable theexisting DCI format for cross link scheduling and, in particular, forthe uplink in-band cross link band configuration to be reused. Todistinguish XCI and DCI, the XL-RNTI may be used (e.g. considered).

According to an embodiment, the inclusion of XCI may enable more PDCCHcapacity and may also increase the UE blind decoding effort, but the lowlatency and robustness of PDCCH may be beneficial for the C-XLDPCscheme. The network may use cross link CSI reports on PUCCH and PUSCH tohelp determine the TF. For example, the cross link CQI may bemultiplexed with PUSCH when an uplink grant may be available. Thenetwork may pre-allocate an uplink grant when requesting the XL CQI inPDCCH. The XL CQI may also be transmitted in PUCCH similarly as DL CQIreporting. A format (e.g. a new format) of PUCCH may be assigned for theXL CSI or PUCCH format 2 may be reused.

Additionally, in an embodiment, the D-XLDPC scheme may not use XCI onPDCCH, as the TF information may be exchanged on the cross link betweenthe UEs. Instead, the TF information may be carried in XCI on the XPCCH.The cross link CSI that may be carried on XPCCH may be used to determinethe TF. However, such an embodiment, may use and/or have some networkscheduling functionality that may reside in the UEs.

A path loss (PL) estimation may be made and/or used. The cross link pathloss (PL) may be estimated by the UE and applied in the powercalculation without reporting it to the network in both C-XLDPC andD-XLDPC. The PL may be estimated by UEs with the help of measurementsbased on factors as described below.

In one example factor, the measurements may be based on neighbordiscovery beacon detection. The ND beacon may be transmitted with acell-specific configured power level, which combined with the detectedbeacon level may vie the path loss. The neighbor discovery may betriggered by pre-defined events, e.g. the path loss updates or it may bea periodical update. In embodiment, the ND beacon level may be broadcastto the UEs.

In another example factor, the measurement may be a cross link referencesignal measurement. The cross link reference signal may be configured totransmit at a known level and combined with the received signal strength(e.g. measurement may use further investigation with more details) itmay give the path loss. This may also use the cross link referencesignal to be transmitted with a known level signaled, e.g., viadedicated RRC signaling or MAC signaling from the network or thecross-link. In the C-XLDPC scheme, it may be signaled in similar to theCRS power level of the reference cell that may be used in the path lossestimation for the uplink power control. In the D-XLDPC scheme, thereference signal level may be included in the cross link grant in thesemi-static scheduling or separately signaled. Additionally, the pathloss may be compensated for in both XPCCH and XPDCH transmit power.

As described herein, transmit power commands may be provided and/orused. The TPC commands may be applied in accumulative and absolutemodes. The accumulative commands may be relative to the previoustransmit power and the absolute commands may be relative to the baseoperating point (e.g. more suitable for intermittent UE transmission).The cross link power step size may be similar to a base line such as anLTE baseline, i.e. {−1, +1} dB and {−1, 0, +1, +3} dB for theaccumulative mode and {−4, −1, +1, +4} dB for the absolute mode.Different step sizes may be also adopted, e.g. a 2 dB step size.

In the C-XLDPC, the TPC bits may not be transmitted on the cross linkand may be transmitted from the eNB in the LTE downlink in the XCItogether with the scheduling information, e.g. reusing DCI format 0 orDCI format 4 where uplink grants may be sent along with the TPC bits.These TPC may be applicable for the XPDCH. As mentioned earlier, the XCImay be decoded using C-RNTI or XL-RNTI. In another example, it may be ina dedicated XCI format for TPC transmission, e.g. reusing DCI format3/3A decoded by TPC-PUSCH-RNTI/TPC-PUCCH-RNTI. The XL can apply alsoTPC-XPDCH-RNTI and TPC-XPCCH-RNTI when decoding the XCI.

In the D-XLDPC scheme, the TPC bits may be transmitted in XPCCH or in aseparate non-power-controlled type of XPCCH using the maximum cross linkpower, or other specified initial cross link power configured by higherlayers. A separate non-power-controlled XPCCH may be used to helpprevent potential race conditions where both UEs may send TPC commandsto regulate the XPCCH carrying the TPC.

In the C-XLDPC scheme, a network component such as an eNB may determinethe TPC based on the received SINR of the cross link reference signal.Such a measurement (e.g. the SINR) may be already used by cross linkmobility and may be available for TPC derivation. Additionally, such ameasurement may be an RRC type measurement request and configured by theeNB. The averaged and filtered result associated therewith may bereported in PUSCH in the form of MAC PDU. In an embodiment, the networkmay also assign an uplink grant for the measurement report at therequest of RRC.

According to an additional embodiment, the TPC may be based on the BLERof the XPDCH. Such a measurement (e.g. the BLER that may be used) may bea periodical BLER counting based on XPDCH ACK and/or NACK. In thisembodiment, the C-XLDPC may be applied in connection with thecentralized dynamic scheduling where the ACK and/or NACK of XPDCH may bereported to the eNB. The BLER may be derived from the XL HARQacknowledgement. In an example embodiment, the BLER may be an RRC typemeasurement request and configured by the eNB. The averaged and filteredresult may be reported in PUSCH in the form of MAC PDU.

Furthermore, in the C-XLDPC, a UE may determine the TPC based on themeasurements described above along with an eNB power control algorithmthat may be implemented in the UE. For example, the TPC may be primarilyused to dynamically adjust the operating point and may not beperiodical. As such, the TPC rate may be adjusted according to the powercontrol algorithm.

Alternatively or additionally, in an embodiment, the TPC may be receivedfrom either a downlink channel or a cross-link channel. For example, theD-XLDPC may be in charge of the path loss and local interferencecompensation while the C-XLDPC may be in charge of interferencecompensation at a larger level (e.g. the eNB may use measurement reportsfrom a set of UEs involved in concurrent D2D links). In that embodiment,one or more rules may be defined to avoid possible races between the twoschemes. For example, the eNB may decide to decrease the power (e.g.because of its own knowledge of the cell interference level) while theD-XLDPC may increase the current power (e.g. because of current D2D linkstatus).

According to an example embodiment, a selected granularity based on orin terms of measurement periodicity, update rate, and/or power step maybe different for the schemes. For example, the C-XLDPC scheme mayprovide updates at a slower rate and with a coarser power stepgranularity than the D-XLDPC scheme where such updates may be periodicor aperiodic. Additionally, the C-XLDPC scheme may define an operatingpower level respecting the general interference level while the D-XLDPCworks around this power level to manage path loss and local interferencevariations.

According to a further embodiment, when a TPC may be provided by theeNB, the D-XLDPC may be interrupted during a given period. If theD-XLDPC may follow an accumulation strategy, an accumulation may bereset (e.g. at this point). In an embodiment, the accumulation strategymay include or refer to a dynamic offset parameter such as a TPC_(XL) asdescribed herein. In the accumulation mode or strategy, the computationof a TPC may rely on its precedent value (TPC_(XL) (i−1)) whereas in theabsolute mode, the computing of a TPC may be an absolute offset that maybe applied. The mode (e.g. accumulation or absolute) that may be usedmay be provided by higher layers. The eNB may also provide a Txreference power in the TPC. At the end of the period, the D-XLPC mayrestart from the new operating point defined by the C-XLDPC.

Additionally, the length of the interruption period may be defined basedon the C-XLDPC strategy and implementation to avoid transient effectsgenerated by the power update (e.g. it may be a static parameter definedby design or provided by RRC or a dynamic parameter provided in theTPC). For example, the eNB may use a few subframes to provide TPCs toseveral UEs and may want to make sure that each updated power level mayhave been applied before running D-XLDPC for each link again. This mayavoid wasting bandwidth for crosslink TPCs working on transientinterference levels and/or avoid getting divergence in the algorithmresults. To respect such a rule, different UEs that may be used orinvolved in a D2D link may decode the TPCs that may be received on thedownlink channel so they may be aware of the C-XLDPC and D-XLDPC (e.g.this TPC may be multi-casted on XL-RNTI).

In some embodiments, the eNB may decide to not interrupt the D-XLDPC(e.g. if there may be one D2D link that may be impacted by C-XLDPC).According to such an embodiment, UEs such as the D2D link UEs may stillfollow other rules (e.g. accumulation reset, new Tx reference, and thelike that may be used or provided as described herein) at the subframethat may be defined for the TPC application.

The TPC that may be received on a downlink channel may indicate one orseveral targeted transmitting UEs. These targeted UEs may be Tx UEs(e.g. as described herein, for example, in the following procedures,actions, or methods). Additionally, other UEs (e.g. that may be involvedor used in the D2D link) may be Rx UEs. According to an exampleembodiment, the Tx and/or Rx modes associated with the UEs may bedefined within the TPC context.

For example, a UE involved in a D2D link may scan any TPC sent ondownlink channel. Additionally, when a TPC targeted to its D2D link maybe identified (e.g. through XL-RNTI), a UE may perform one or more ofthe following. A UE may identify if a TPC such as a downlink TPC commandmay indicate or signal whether the UE may be a Tx or Rx UE. According toan example embodiment, this may be performed or done, for instance, bydetermining whether the RNTI that may be used to mask the CRC of the DCIthat includes the command corresponds to the link in which the UE may bethe receiver or the transmitter.

If the UE may be a Tx UE, the UE (e.g. the Tx UE) may update its Txpower (e.g. in a relative or absolute mode) based on the downlink TPCcommand and may ignore a crosslink TPC command during a period of Nsubframes where N being defined in the TPC command or preliminaryprovided by higher layers). Alternatively or additionally, the UE maystart a prohibit timer of a pre-determined or configured duration. TheUE may act on the crosslink TPC commands if the prohibit timer may notbe running.

If crosslink accumulation mode may be enabled, a Tx UE may reset it.Additionally, if the UE may be a Rx UE, the UE (e.g. the Rx UE) may stoptransmitting a crosslink TPC command to a Tx UE(s) during the period ofN subframes. Alternatively or additionally, the UE may start a prohibittimer of a pre-determined or configured duration. The transmission ofTPC command may occur if the prohibit timer may not be running.

Also, if a UE may be an Rx UE, the Rx UE may update the Tx referencepower based on a value indicated in the downlink TPC for its path losscomputation. After the N subframes, the Rx and Tx UEs may restart thesend and decode crosslink TPCs

A derivation from UL power control may be provided and/or used asdescribed herein. For example, the transmission power used for at leastone XL channel or signal, or the sum thereof, may be tied to thetransmission power used for an UL channel or signal such as PUCCH, PUSCHor SRS, or to parameters and variables that may be used in thecalculation thereof. The UL channel may be a channel in the serving cellin which the cross-link transmission may be taking place. Such linkagebetween the powers used for XL channels and UL channels may protect a ULoperation in the network by limiting interference that may be caused toUL transmissions in the same serving cell or neighboring serving cells.

In an embodiment, the transmission power of the at least one XL channelor signal (PXL) may be derived from the transmission power of at leastone UL channel or signal as described herein. For example, according toan embodiment, the nominal cross link maximum transmission power (e.g.,P_(CMAX,XL)) may be derived from the transmission power of at least oneUL channel or signal. In such an embodiment, the actual transmissionpower that may be used for an XL channel or signal (e.g., such as XPCCHor XPDCH) may be determined according to at least one of the solutionsor embodiments described herein (e.g. above) with the parameterP_(CMAX,XL) derived from UL power control as described herein (e.g.below). In particular, the power headroom applicable to the XL channel(or combination thereof) may be calculated with P_(CMAX,XL) derivedusing such an embodiment. Additionally, such an embodiment may allow orenable the use of a transmission power even smaller than what may beused to protect UL operation, which may be beneficial to reduceinterference to other cross-links potentially using the same resourcesin the network.

Additionally, in the embodiments described herein, the derivation of thetransmission power of an XL channel or signal (P_(XL)), or of thenominal cross link maximum transmission power (P_(CMAX,XL)) may beperformed according to at least one of the following. For example, inone embodiment, P_(XL) or P_(CMAX,XL) may reuse at least one of the pathloss measurement (PL_(c)) and power control adjustment state (f_(c)(i))components of the transmit power of an UL channel.

In such an embodiment, P_(XL) or P_(CMAX,XL) may be expressed as thefollowing for subframe iP _(XL)(i)=min{P _(XL) _(_) _(MAX)(i),P _(OFFSET,XL)(i)+α_(c)(j)·PL _(c)+f _(c)(i)}orP _(CMAX,XL)(i)=min{P _(XL) _(_) _(MAX)(i), P_(OFFSET,XL)(i)+α_(c)(j)·PL _(c) +f _(c)(i)}where α_(c)(j) may be a parameter used in the derivation of transmitpower for PUSCH, PL_(c) may be the downlink pathloss estimate that maybe calculated in the UE, and f_(c)(i) maybe the PUSCH power controladjustment state in subframe i. Alternatively or additionally, the PUCCHpower control adjustment state g(i) may be used in place of f_(c)(i) forat least one cross-link channel or signal. These values may be for aserving cell (c) that may be the serving cell whose UL resources may beused for the cross link transmissions, and the index j may be fixed to aspecific value (e.g. 0). In such an embodiment, P_(XL) _(_) _(MAX)(i)may be a configured maximum transmit power and P_(OFFSET,XL)(i) may be aparameter that may be derived from at least one of: at least oneparameter that may be received from higher layers, such as an offsetP_(0,OFFSET,XL) and at least one property of the cross link transmissionin subframe i, such as the bandwidth, the number of code blocks, thenumber of control information bits, the number of information bits, thetransmission format, and the like. For example, in an embodiment,P_(OFFSET,XL)(i) may be determined as the sumP_(0,OFFSET,XL)+Δ_(TF,XL)(i) where Δ_(TF,XL)(i) may be calculatedaccording to embodiments described herein (e.g. above).

In another example, the path loss measurement may be reused while thepower control adjustment state TPC_(XL) may remain specific to thecross-link and may be obtained using one of the embodiments describedherein above, and.P _(XL)(i)=min{P _(XL) _(_) _(MAX)(i), P _(OFFSET,XL)(i)+α_(c)(j)·PL_(c)+TPC_(XL)}orP _(CMAX,XL)(i)=min{P _(XL) _(_) _(MAX)(i), P_(OFFSET,XL)(i)+α_(c)(j)·PL _(c)+TPC_(XL)}

Dependency from the latest transmission power that may be used for adiscovery signal may be provided and/or used. For example, thetransmission power used for at least one cross-link channel or signalmay be tied to the transmission power P_(DIS). According to anembodiment, the P_(DIS) may have been used for the latest transmissionof a specific discovery signal that may be associated to this cross-linkchannel. For instance, the transmit power may be determined according toP _(XL)(i)=min{P _(XL) _(_) _(MAX)(i), P _(DIS) +P _(OFFSET,XL)(i)+TPC_(XL)}where P_(OFFSET,XL)(i) may be determined according to a solution similarto the embodiments described herein. In such an example, the UE initialtransmit power may be determined based on P_(DIS) and an adjustmentP_(0,OFFSET,XL)(i) that may depend on the nature of the cross-linktransmission and/or may be subsequently be adjusted based on TPCcommands.

In embodiments, multiple power control modes may also be provided and/orused. For example, a solution or embodiment used for determining thetransmission power of a cross-link channel or signal (or power controlmode) may depend on at least one of the following: the resource in whichthe cross-link transmission may occur (e.g. expressed in terms ofsubframes, carrier, or resource block allocations that may besemi-statically or dynamically allocated by the network); the UE withwhich the cross-link transmission may occur; the type of cross-linkchannel or signal transmitted (e.g. control channel, data channel orreference signal); an explicit configuration signaled by the network;and the like.

Such different solutions or embodiments may facilitate efficientutilization of network resources for D2D communications. For example,the UE may use a power control mode where the transmit power or maximumtransmit power of a cross-link channel may be derived from the uplinkpower control parameters, as described herein (e.g. above), in subframeswhere regular uplink transmissions may also occur from the same or otherUEs in other resource blocks of the uplink carrier. On the other hand,the UE may use a power control mode independent of uplink power controlin subframes where no regular uplink transmission may occur, possiblyfor a group of cells. For example, the UE may be configured to use asemi-statically configured transmit power in certain subframes.

In embodiments, where multiple power control modes may be simultaneouslyconfigured to a UE, for example, as described herein, a power controladjustment such as one or more TPC commands may be associated to aspecific power control mode and may be used to affect the adjustmentstate of this particular mode. One or more parameters that may be usedin a power control mode such as TPC step size adjustment may bespecifically configured for this mode. Additionally, more than one powercontrol mode may be configured that may use the same formulas and updateprocedures, but, for example, different values for the associatedparameters.

In example embodiments, the power control mode to which the TPC commandmay be associated may depend on which channel or if applicable DCIformat the TPC command may be received from, whether the command may bereceived from the serving cell or another UE, and of which UE, thesubframe in which the TPC command may be received, and the like.

The UE may also report power headroom (e.g. separately) for each powercontrol mode. Additionally, the UE may trigger transmission of a reportwhen the transmission power for a given power control mode may exceed athreshold, or when the power headroom may become or may be lower than athreshold. The report may include a power headroom report signaled atthe MAC layer, or of a measurement report signaled at an RRC layer. Inexample embodiments, the threshold may be provided by higher layers.

According to an embodiment, XL power headroom reporting may also beprovided and/or used. For example, the XL power headroom may be ameasure of the difference in one sub-frame between the P_(CMAX,XL) andthe power-controlled XPDCH transmit power P_(XPDCH) that may be used ifthere may be no limit of the XL transmit power (e.g. as shown in theequation below).XLPH(i)=P _(CMAX,XL)(i)−(10 log₁₀(BW _(XPDCH)(i)+P _(O) _(XPDCH)+α_(XL)PL+Δ_(TF) _(XL) ₍ i)+TPC _(XL)) [dB]The foregoing parameters have been discussed in connection with crosslink nominal maximum power determination, cross link maximum powercontrol, and the XPDCH power control.

In the C-XLDPC, the eNB may evaluate the cross link scheduling decision,for example, to improve or optimize the combination of MCS and bandwidthin the cross link grant with the help of the XPDCH power headroomreporting performed by UE MAC layer. This power headroom may be similarto the current power headroom that may be applied in the uplink whichmay be calculated for one sub-frame.

The XLMPC may take the cross link headroom reporting as an input, butgiven the semi-static nature, an averaged power headroom may be reportedon a sub-frame basis. This may be applied in the D-XLDPC where, forexample, the granted cross link bandwidth may be similar or the sameduring the semi-static cross link grant and the UEs schedule MCS anddetermine TPC autonomously. Given the constant bandwidth, the long-termaverage power headroom may be used to illustrate or show how power maybe utilized in the cross link.

In both C-XLDPC and D-XLDPC schemes, the power headroom may be reportedto the network. The long-term average power headroom may be reportedsimilarly as the short-term power headroom in the MAC Control Element.The existing MAC control element for PHR, for example, the ExtendedPower Headroom MAC Control Element may be used to report the XL PHR. TheXL PHR may be concatenated with the PHR for Pcell and Scells in the CAconfiguration. When a UE may not be configured with CA, the extended MACCE may further be applied.

Additionally, in example embodiments, various types of power headroommay be used and/or provided in addition to a Type 1 and Type 2 PH andthe power headroom types for both UL and XL may be one or more of thefollowing: a Type 1 PH with a UE transmitting PUSCH; a Type 2 PH with aUE transmitting PUSCH and PUCCH simultaneously; a Type 3 PH with a UEtransmitting XPDCH; Type 4 PH with a UE transmitting XPDCH and XPCCHsimultaneously; and the like.

The XLPHR may also be triggered by a significant change in estimatedcross link path loss since the last XLPHR. For example, a similarPathLossChange of phr-Config structure in IE MAC-MainConfig may bereused for the cross link. The XLPHR may further be triggered when morethan a configured time may have elapsed since the last XLPHR, forexample, when a timer for XLPHR may have lapsed. In an additionalexample, the XLPHR may be triggered when more than a configured numberof closed-loop cross link TPC may have been implemented by the UE. Suchan XLPHR may be, for example, unilateral. According to another oradditional embodiment, the XLPHR may be triggered when long-term averageXLPHR may have exceeded a pre-set hysteresis. For example, the long-termaverage XLPHR may have been trending in certain negative range and themaximum cross link power may be increased.

The XLPHR may also periodical to facilitate the XLMPC, for example, forthe case where the granted bandwidth may be applied unchanged. Theseconfigurations may be included in the PHY MAC configuration for thecross link.

UE transmit timing alignment may also be provided and/or used. Forexample, when UEs (e.g. two UEs) may operate in the AT applications, theUE-to-UE link may operate the cross link according to its own time linewith reference to the downlink or uplink timing. For example, the UEsmay align the cross link transmit timing with the uplink (e.g. LTEuplink) transmit timing. In an embodiment, aligning the cross linktransmission with the uplink transmission may help reduce prevent theuplink transmission of a subsequent sub-frame from overlapping with thecross link transmission of the previous sub-frame due to the timingadvance (TA). The maximum TA may be 0.67 ms and, therefore, for acell-edge UE's uplink transmission, scheduled in sub-frame X, mayactually start as early as 0.67 ms before the start of sub-frame X (e.g.0.33 ms after the start of sub-frame X-1). If this UE may also operatethe cross link transmission in sub-frame X-1 and the cross linktransmission timing may be aligned with the downlink timing, the crosslink transmission may be impacted by interference. The inadvertentuplink bleeding into the cross link transmission may be avoided orreduced when a UE may transmit its UL and XL with the same timing.

To facilitate the receiver with the cross link transmission, both UEsmay transmit the XLRS once the cross link may be established and theresource may be allocated. The transmit timing of the XLRS may followthe uplink timing, which may be downlink timing plus the TA. Based onthe low mobility and close proximity, their downlink timing may be closeto each other, because both may be synchronized with a common downlinktiming reference (e.g. the serving cell's Cell-specific Reference Signal(CRS)). In an embodiment, for a UE to receive the XLRS, it may factor inthe TA of the other UE.

Additionally, in an embodiment, the network may inform or signal to bothUEs of each other's TA when setting up the cross link (e.g. to help withtransmit timing alignment). Additionally, the network may apply a newtype of MAC CE reusing the structure of the timing advance command MACCE.

The UE may also apply its own TA such that the UE may align its receiverusing its own downlink timing plus its own TA. In such an embodiment,given the close proximity, the two UEs may experience highly correlatedpropagation conditions in the uplink such that their TAs may be close toeach other.

In either embodiment, the UE may apply a small-size searching windowaround its own uplink timing to locate the start the reference signal,i.e. the transmission timing. Once it may be found, the cross linkreceiver may lock onto the timing by fine-tracking of the XLRS. Thenetwork may also keep informing the TAs to both UEs to maintain thetiming alignment. When using the downlink timing for transmission on thecross link, the bleeding issue from uplink to the cross link due to theTA may be difficult to resolve.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A method of controlling a cross link transmitpower level on a wireless transmit/receive unit (WTRU), the methodcomprising: selecting a cross link transmit power control (TPC) formulafor a cross link transmission from the WTRU to another WTRU, wherein thecross link TPC formula is selected from at least a first cross link TPCformula and a second cross link TPC formula, wherein the first crosslink TPC formula is based on a bandwidth of the cross link transmissionand path loss information; determining a cross link transmit power levelin accordance with at least the selected cross link TPC formula; andsending, by the WTRU to the other WTRU, the cross link transmission witha cross link transmit power set to the determined cross link transmitpower level, wherein the first cross link TPC formula is associated witha first cross link power control mode and the second cross link TPCformula, is associated with a second cross link power control mode. 2.The method of claim 1, wherein the cross link transmit power level iscontrolled on a per-transmission time interval (TTI) basis.
 3. Themethod of claim 1, further comprising receiving, by the WTRU, anexplicit indication in downlink control information, the explicitindication indicating the second cross link TPC formula.
 4. The methodof claim 3, wherein: the DCI includes a TPC command; and the explicitindication is included in the TPC command.
 5. The method of claim 1,wherein the cross link transmit power level is determined in connectionwith a transmission power level of an uplink (UL) channel between theWTRU and a network entity.
 6. The method of claim 3, further comprisingdetermining the first one of the plurality of cross link power controlmodes for use by the WTRU, wherein the first one of the plurality ofcross link power control modes is associated with the received explicitindication.
 7. The method of claim 1, wherein the first cross link TPCformula is selected in accordance with the first one of the plurality ofcross link power control mode.
 8. The method of claim 1, furthercomprising receiving an indication from a network entity, wherein thesecond cross link TPC formula is selected from a plurality of cross linkTPC formulas based on at least the received indication.
 9. The method ofclaim 1, wherein the selected cross link TPC formula is one of: (1)calculated based on the bandwidth associated with the cross linktransmission and the path loss information or (2) used semi-staticallyfor more than one subframe.
 10. The method of claim 1, wherein the crosslink transmit power level in the first cross link TPC formula isdetermined based on the path loss information, the bandwidth associatedwith the cross link transmission and one or more parameters obtained viahigher layer signaling.
 11. A wireless transmit/receive unit (WTRU)comprising: a transmitter; a receiver; and a processor, operably coupledto the receiver and the transmitter, configured to: select a cross linktransmit power control (TPC) formula for a cross link transmission fromthe WTRU to another WTRU, wherein the cross link TPC formula is selectedfrom at least a first cross link TPC formula and a second cross link TPCformula, wherein the first cross link TPC formula is based on abandwidth of the cross link transmission and path loss information, anddetermine a cross link transmit power level in accordance with at leastthe selected cross link TPC formula; and the transmitter configured tosend to the other WTRU the cross link transmission with a cross linktransmit power set to the determined cross link transmit power level,wherein the first cross link TPC formula associated with a first crosslink power control mode and the second cross link TPC formula isassociated with a second cross link power control mode.
 12. The WTRU ofclaim 11, wherein the processor is configured to control the cross linktransmit power level on a per-transmission time interval (TTI) basis.13. The WTRU of claim 11, wherein the receiver is configured to receivean explicit indication in downlink control information (DCI), theexplicit indication indicating the second cross link formula.
 14. TheWTRU of claim 13, wherein: the DCI includes a TPC command; and theexplicit indication is included in the TPC command.
 15. The WTRU ofclaim 11, wherein the processor is configured to determine the crosslink transmit power level in connection with a transmission power levelof an uplink (UL) channel between the WTRU and a network entity.
 16. TheWTRU of claim 13, wherein the processor is configured to determine thefirst one of the plurality of cross link power control modes for use bythe WTRU, wherein the first one of the plurality of cross link powercontrol modes is associated with a received explicit indication.
 17. TheWTRU of claim 11, wherein the first cross link TPC formula is selectedin accordance with the first cross link power control mode.
 18. The WTRUof claim 11, wherein the receiver is configured to receive an indicationfrom a network entity, wherein the second cross link TPC formula isselected from a plurality of cross link TPC formulas based on at leastthe received indication.
 19. The WTRU of claim 11, wherein the processoris configured to one of: (1) calculate the selected cross link TPCformula based on the bandwidth associated with the cross linktrabsmission and the path loss information or (2) use the selected crosslink TPC formula semi-statically for more than one subframe.
 20. TheWTRU of claim 11, wherein the processor is configured to determine thecross link transmit power level in the first cross link TPC formulabased on the path loss information, the bandwidth associated with thecross link transmission and one or more parameters obtained via higherlayer signaling.